Preparing Parts For Local Case-hardening

At the works of the Dayton Engineering Laboratories Company, Dayton,
Ohio, they have a large quantity of small shafts, Fig. 40, that
are to be case-hardened at A while the ends B and C are to
be left soft. Formerly, the part A was brush-coated with melted
paraffin but, as there were many shafts, this was tedious and great
care was necessary to avoid getting paraffin where it was not wanted.

To insure uniform coating the device shown in Fig. 41 was made.
Melted paraffin is poured in the well A and kept liquid by setting
the device on a hot plate, the paraffin being kept high enough
to touch the bottoms of the rollers. The shaft to be coated is
laid between the rollers with one end against the gage B, when
a turn or two of the crank C will cause it to be evenly coated.